In general, in formulating cosmetics which are directly applied to a human skin for supplying moisture, oil and the like in a hygienic manner, it is necessary to conduct strict and scientific study and examination of the constituent to be used and the processing techniques to be employed.
The surface of human skin is protected by sebum secreted from sebaceous glands. The sebum not only contributes to protect the skin from external physical and chemical stimulations, maintaining the skin in a physiologically normal state irrespective of environmental conditions, but also plays an important role in preventing invasion of harmful microorganisms. Therefore it has been a matter of great concern for cosmetic chemists to find materials which have behaviors similar to those of the sebum as cosmetic constituent.
Each raw material for a safe cosmetic having excellent properties should meet the following requirements:
It should be non-irritant.
It should by physically stable, that is, it should not solidify even at low temperatures.
It should exhibit no biodegradability. In other words, it should be free from the contamination of germs.
It should be chemically stable without undergoing hydrolysis.
It should have low oral and percutaneous toxicity.